1. Field of the Invention
The invention relates to an article turner assembly for turning conveyed articles. More particularly, the invention relates to an apparatus and method for the in-line turning of selected articles as those articles are conveyed along a path of conveyance. The invention additionally relates to an apparatus and method for the high speed palletizing of articles using such an article turner assembly.
2. Background of the Invention
Article turner assemblies are well known for turning conveyed articles, i.e., for rotating the articles a designated amount, usually 90.degree., as they are conveyed along a path. Article turner assemblies have many applications in a variety of article handling applications. For instance, an articles turner assembly often is used as part of a pattern former of a palletizer. Palletizers are well-known for automatically or semi-automatically stacking layers of articles such as cartons or bags on a pallet, sheet, or other support. The typical palletizer includes vertically-spaced upper and lower conveyor assemblies which convey articles and supports, respectively.
The lower conveyor assembly of the typical palletizer includes a vertically-movable hoist (sometimes known as an indexing pallet hoist) that is raiseable to receive layers of articles one at a time from the upper conveyor assembly to form a stack and that indexes downwardly to receive each successive layer. The lower conveyor assembly may also include an outfeed conveyor for conveying a full stack away from the hoist as well as a staging mechanism and other equipment for conveying a stack of pallets, sheets, or other supports towards the hoist and for delivering the supports one at a time to the hoist.
The upper conveyor assembly of the typical palletizer is designed to 1) receive articles from an infeed conveyor, 2) form layers of articles suitable for stacking, and 3) deposit the layers one at a time onto the underlying indexing hoist. Cartons and most other articles typically are rectangular rather than square in shape. Secure stacking of these articles in layers usually requires that each layer of articles take the form of a pattern in which the articles have more than one orientation. Patterns are usually formed by turning some articles 90.degree. as they are conveyed along the upper conveyor assembly. As a result of this pattern formation, each article of each successive layer can be supported by two or more articles of an underlying layer to form a more secure stack by interweaving the layers.
Article patterns are typically formed by a pattern former comprising an article turner assembly, a sorter, and an accumulator. The article turner assembly and sorter, in combination, divide a lane of incoming articles of common orientation into multiple lanes of articles in which at least some of the articles in at least one of the lanes is turned so as to be orientated differently from some of the articles in the remaining lanes. The lanes of articles are accumulated in the accumulator to form the patterns.
The article turner assembly of the pattern former is usually located downstream of the sorter because, unless they are activated and deactivated, most article turner assemblies are incapable of selectively turning articles in a given path while letting other articles pass along that path without being turned. This is particularly true in the case of high speed palletizers and other high speed article handling applications. If the operative component of the article turner assembly were located downstream of the sorter, the operative component would have to somehow be selectively activated and deactivated to effect the selective article turning required for pattern formation. This activation requirement would necessarily reduce the speed at which layers could be formed and is typically avoided by placing the article turner upstream of the sorter. Palletizers having some or all of these characteristics are disclosed, for example, in U.S. Pat. No. 2,947,405 to Fenton; U.S. Pat. No. 3,523,601 to Roth et al.; U.S. Pat. No. 4,026,422 to Leenaards; U.S. Pat. No. 3,954,190 to Howard et al.; and U.S. Pat. No. 5,320,478 to Gonowski et al.
Article turner assemblies used in palletizers and other article handling applications exhibit characteristics rendering them disadvantageous for use in many applications.
For instance, most article turner assemblies require contact between the operative element of the article turner assembly and a front and/or side surface of the article to turn the article. An example of an article turner assembly of this type is the so-called "bump" or "turnpost" turner an example of which is disclosed in U.S. Pat. No. 4,026,422 to Leenaards. In this type of article turner assembly, the article is conveyed so that the front surface of the article contacts a vertically-extending stationary turnpost and spins about the turnpost to effect the desired 90.degree. of article rotation. The article impacts the turnpost with substantial force when the article is conveyed at high speeds. In the usual case in which the article comprises a package containing goods, this impact may result in substantial abrasion or other marring of the package and may damage goods stored in the package. Moreover, article turner assemblies of this type cannot operate on articles in a true in-line fashion because the spinning or rotation of the conveyed article about the stationary turnpost necessarily decelerates the article as it is turned. This deceleration necessarily reduces the maximum speed at which patterns can be formed with resultant reduction in the speed of downstream operations such as stacking. This characteristic of turnpost turners is problematic because high speed operation is becoming an increasingly-important concern in nearly every aspect of article conveyance. Any article turning operation that results in substantial article deceleration therefore is undesirable because it causes a bottleneck in the article handling process.
Some article turner assemblies are capable of turning articles without contact with a front or side surface of the article and hence present a lower risk of damage to conveyed articles. However, no previously-known article turner assembly of this type is capable of selectively and rapidly turning articles so as not to form a bottleneck in the article handling system and so as not to require multiple lanes for turned and unturned articles.
For instance, U.S. Pat. No. 3,580,379 to Shuster et al. discloses an article turner assembly that turns articles by shifting conveyor sections or carriers laterally relative to one another so that a front portion of the turned article is conveyed in one direction by a first series of carriers while the rear portion of the same article is supported on carriers which move in a different direction. The articles therefore simultaneously change orientation and change lanes. The speed of article turning necessarily is limited by the speed at which the carriers can be shifted. The resultant system is relatively complex and slow-acting.
Similarly, U.S. Pat. No. 5,195,627 to Wyman discloses an article turner assembly that relies on a speed differential between two sets of adjacent roller conveyors to turn articles. The speed of each set of roller conveyors is constant, and all articles on a particular path always contact all rollers in that path. Therefore, all articles conveyed along a particular path are either turned or not turned. The article turner assembly of the Wyman patent therefore must be located downstream of a sorter or lane former. System versatility therefore is substantially reduced and system complexity is substantially increased.
Still another example of an article turner assembly lacking a turnpost or similar structure is disclosed in U.S. Pat. No. 5,383,760 to Cawley et al., which relies on a speed differential between two parallel belt conveyors to turn articles. All conveyed articles are turned (assuming a designated speed differential exists between the two belts). System versatility therefore is substantially reduced compared to multi-lane systems.
At least one proposal has been made to selectively either turn or not turn articles without requiring a major path change of the conveyed articles for turning selection. Specifically, U.S. Pat. No. 4,024,965 to Marth et al. discloses a bag palletizer having an article turner assembly employing a turnpost as its operative element or article turner. A movable deflector bar is provided upstream of the turnpost to selectively either direct articles into engagement with the turnpost to turn them or to deflect articles around the turnpost so that they continue downstream without being turned. While this arrangement lacks some of the disadvantages of other, multiple-lane article turner assemblies, it still requires a substantial change in the direction of article conveyance depending on whether or not the article is turned. This change of direction necessarily increases the length of time required for an article to traverse the article turner assembly and reduces the maximum available speed for downstream operations such as pattern forming and palletizing. In addition, because a relatively long deflector bar is required to deflect unturned articles past the turnpost, articles must be conveyed through the article turner assembly with a substantial spacing that is at least as long as the deflector bar. This requirement additionally reduces the maximum speed of the article turner assembly. Moreover, by using a turnpost to effect article turning, the system of the Marth et al. patent exhibits all of the other disadvantages described above with respect to turnpost-based systems.